The present invention relates to a technique for reserving a resource to be used in a future communication in accordance with a request from a user terminal in a network to which a plurality of switching nodes each linking a plurality of user terminals are connected. More particularly, the invention relates to a method of reserving a network resource such as a network band and a communication quality level in a computer network in which a plurality of network nodes are connected.
With improvement in computer technology and communication technology, the desire for real-time communication of audio data and video data is becoming stronger. Especially, in a network such as the internet which does not guarantee the communication quality, such a request is becoming stronger.
In order to perform the real-time communication, it is necessary to assure dedicated resources at the time of communication. As a resource reservation protocol in the internet, the resource reservation protocol (RSVP) is being examined by the internet engineering task force (IETF).
In a new network such as ATM, when a communication is started, resources for satisfying the communication quality adapted to the kind of communication are preliminarily assured by the signalling protocol Q.2931 and the communication is performed.
In the foregoing conventional techniques, it is necessary for a user terminal to issue a request for assuring the resource at the start time point of the communication. Even when the start time and end time of the communication are preliminarily known, the resources used during the communication cannot be preliminarily assured.
For example, with respect to a communication requiring a real-time performance such as a television conference whose holding time is preliminarily known, when the resource has been already assured by another communication at the start time point of the communication, a problem such that the sufficient quality of the communication cannot be guaranteed occurs.
Especially, in order to transmit multimedia data without interruption in an open network environment represented by the internet, it is necessary to assure the communication quality desired by the user in such a manner that switching nodes on a communication path assure resources necessary for the multimedia communication. As a technique for achieving the object, a communication protocol called a resource reservation protocol is examined in the above-mentioned internet engineering task force.
In the ATM (Asynchronous Transfer Mode) network, by designating the requested communication quality, band, and the like at the time of a setting of ATM switching devices as nodes in the network, the desired communication quality can be assured.
In the conventional techniques, the communication protocol for assuring the necessary network resources at the time of an actual communication is specified. Consequently, the network resource cannot be reversed until the start of the communication.
In order to reserve the network resource in the conventional techniques, a high degree of knowledge regarding the network resource is necessary. An end user of the network cannot easily reserve it.
Further, since the reservation state of the network resource cannot be known in the conventional techniques, it is difficult to try to reserve other resources by changing the conditions.
In the conventional techniques, further, there is not provided a method of permitting or rejecting a reservation by totally discriminating information such as the network use right of the user, priority of communication, and the like when it is determined whether the network resource can be reserved or not.